Measurement of landing mosquito density on humans

In traditional vector surveillance systems, adult mosquito density and the rate of mosquito-human host contact are estimated from the mosquito numbers captured in mechanical traps. But the design of the traps, their placement in the habitat and operating time, microclimate, and other environmental factors bias mosquito responses such that trapped mosquito numbers may be at variance with the numbers actually making human contact. As an alternative to mechanical traps, direct measurement of landing mosquito density enables real-time estimation of the mosquito–human-host-contact parameter. Based on this paradigm, we studied methods to measure mosquito landing responses to a human host. Our results showed: (a) an 18% difference (P < 0.0001) in the mean number of female Aedes albopictus (Skuse) making initial contact with the skin (9.11 ± 0.74 min–1) compared with the number remaining on the skin for 5 s (7.42 ± 0.69 min–1); (b) an increase (P < 0.05) in the mean per minute (min−1) landing responses of Culex nigripalpus Theobald and Cx. quinquefasciatus Say with increased sampling time; (c) no difference (P > 0.55) in the average number of Ae. albopictus landing on the arm (8.6 ± 1.6 min–1) compared with the leg (9.2 ± 2.5 min–1) of the same human subject; (d) differences among day-to-day landing patterns for the mosquito species we studied but measurable periodicity (P < 0.05) in each case when daily patterns were averaged for four or more diel periods; and (e) an effect on landing mosquito density from air temperature (P < 0.0001) for Ae. albopictus and Cx. nigripalpus and dew point temperature (P < 0.0001) for Cx. quinquefasciatus. Results from this study were used to develop a procedure for safely and accurately measuring mosquito landing density on a human subject.